Abrasive and wear resistant material

ABSTRACT

An abrasive and wear resistant material comprises a mass of carbide particles, a mass of cubic boron nitride particles, and a bonding metal or alloy, bonded into a coherent, sintered form. The cubic boron nitride particle content of the material is from 10% to 18% inclusive by weight, the particle size of the cubic boron nitride is less than 20 micron or less, and the material is substantially free of hexagonal boron nitride. The abrasive material is of particular use in tool components or inserts for application in the abrading of wood and other lignocellulosic materials.

BACKGROUND TO THE INVENTION

[0001] THIS invention relates to an abrasive and wear resistant materialcontaining cubic boron nitride and cemented carbide, and to a method ofproducing the material.

[0002] Cemented carbide is a material which is used extensively inindustry for a variety of applications, both as an abrading material andas a wear resistant material. Cemented carbides generally consist ofsuitable carbide particles such as tungsten carbide, tantalum carbide ortitanium carbide, bonded together by means of a bonding metal such ascobalt, iron or nickel, or an alloy thereof. Typically, the metalcontent of cemented carbides is about 3 to 35% by weight. They areproduced by sintering the carbide particles and the bonding metal attemperatures of the order of 1400° C.

[0003] At the other end of the spectrum, ultrahard abrasive and wearresistant products are found. Diamond and cubic boron nitride compactsare polycrystalline masses of diamond or cubic boron nitride particles,the bonding being created under conditions of elevated temperature andpressure at which the ultrahard component, i.e the diamond or cubicboron nitride, is crystallographically stable. Polycrystalline diamond(PCD) and polycrystalline cubic boron nitride (PCBN) cart be producedwith or without a second phase or bonding matrix. The second phase, whenprovided, may be, in the case of diamond, a catalyst/solvent such ascobalt, or may be a carbide forming element such as silicon. Similarsintering mechanisms are utilised in PCBN synthesis with variouscarbides, nitrides and borides being common second phases.

[0004] PCD and PCBN have a far higher wear resistance than cementedcarbides, but tend to be somewhat brittle. This brittleness can lead toedge chipping of the working surface which can present a problem inapplications where fine finishes are required. Furthermore, ultrahardproducts such as PCD and PCBN can generally not be directly brazed ontoa metallic support. They are therefore often sintered in combinationwith a cemented carbide substrate. The bi-layered nature of suchultrahard products can be problematic in terms of thermo-mechanicalstresses between the two materials: differential expansion and shrinkageon heating and cooling due to different thermal expansion coefficientsand elastic moduli can lead to crack formation or unfavourable residualstresses if the substrate-and the ultrahard products are too dissimilar.Another potential problem of such bi-layered materials is that ofundercutting, i.e preferential wear of the less abrasion resistantcarbide support. Further, machining of ultrahard products is difficultand costly, where carbide products can be relatively easily ground tothe final geometry.

[0005] Efforts have been made to solve some of these problems.

[0006] JP-A-57 116 742 discloses the preparation of a modified cementedcarbide under hot pressing conditions, i.e temperatures of the order of1400° C. to 1500° C. with little or no pressure being applied. These arenot conditions at which cubic boron nitride is crystallographicallystable.

[0007] European Patent No. 0 256 829 describes a method of producing anabrasive and wear resistant material comprising a mass of carbideparticles, a mass of cubic boron nitride particles and a bonding metalor alloy bonded into a coherent, sintered form, the cubic boron nitrideparticle content of the material not exceeding 20% by weight and thematerial being substantially free of hexagonal boron nitride, whichcomprises contacting appropriate amounts of a mass of carbide particlesand a mass of cubic boron nitride particles with a bonding metal oralloy and sintering the particles and metal or alloy under temperatureand pressure conditions at which the cubic boron nitride iscrystallographically stable.

SUMMARY OF THE INVENTION

[0008] According to a first aspect of the invention there is provided anabrasive and wear resistant material comprising a mass of carbideparticles, a mass of cubic boron nitride particles, and a bonding metalor alloy, bonded into a coherent, sintered form, wherein:

[0009] the cubic boron nitride particle content of the material is from10% to 18% inclusive by weight;

[0010] the particle size of the cubic boron nitride is 20 micron orless; and

[0011] the material is substantially free of hexagonal boron nitride.

[0012] According to a second aspect of the invention there is provided amethod of producing an abrasive and wear resistant material includingthe steps of providing a mixture of a mass of discrete carbide particlesand a mass of cubic boron nitride particles, the cubic boron nitrideparticles being present in the mixture in an amount such that the cubicboron nitride content of the material is from 10% to 18% inclusive byweight, and wherein the cubic boron nitride particles have a particlesize of 20 micron or less, and subjecting the mixture to elevatedtemperature and pressure conditions at which the cubic boron nitride iscrystallographically stable and at which substantially no hexagonalboron nitride is formed, in the presence of a bonding metal or alloycapable of bonding the mixture into a coherent, sintered material.

[0013] The abrasive material of the invention or produced by the methodof the invention may be used as an abrasive product for abradingmaterials, or as a wear resistant material, particularly in toolcomponents or inserts which consist of an abrasive compact bonded to acemented carbide support. The abrasive product is of particularapplication in the cutting of wood and like materials.

[0014] Thus, according to a third aspect of the invention there isprovided a method of abrading a workpiece selected from wood and otherlignocellulosic materials including the steps of providing a tool havinga tool component or insert comprised of an abrasive and wear resistantmaterial comprising a mass of carbide-particles, a mass of cubic boronnitride particles and a bonding metal or alloy bonded into a coherent,sintered form, wherein the cubic boron nitride particle content of thematerial is from 10% to 18% inclusive by weight, the particle size ofthe cubic boron nitride is 20 micron or less, and the material issubstantially free of hexagonal boron nitride; providing the workpiece;bringing the tool component or insert into contact with the workpieceand advancing the tool component or insert into the workpiece in anabrading manner.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a graph showing the maximum flank wear of variousmaterials prepared according to Example 1;

[0016]FIG. 2 is a graph showing the maximum flank wear of variousmaterials prepared according to Example 2;

[0017]FIG. 3 is a schematic drawing of a cutter blade design for use inExample 7; and

[0018]FIG. 4 is a graph of tool flank wear as a function of linearmeters machined according to Example 7.

DESCRIPTION OF EMBODIMENTS

[0019] The crux of the invention is an abrasive and wear resistantmaterial which comprises a mass of carbide particles, a mass of cubicboron nitride particles and a bonding metal or alloy bonded into acoherent, sintered form, which is characterised in that the cubic boronnitride particle content of the material is from 10% to 18% inclusive byweight, the particle size of the cubic boron nitride is 20 micron orless, optionally less than 10 micron, and the material is substantiallyfree of hexagonal boron nitride.

[0020] It has been found that the abrasive material of the invention,with a cubic boron nitride particle content in the range of 10% to 18%by weight, provides a material which is optimum in machiningperformance, impact resistance, brazeability and grindability. Lowercubic boron nitride particle contents resulted in wear resistance notmuch better than that of comparable conventional tungsten carbides,while cubic boron nitride particle contents in excess of 18% resulted inreduced brazing strengths, lower impact resistance and increaseddifficulty in tool preparation through grinding.

[0021] In addition, in the abrasive material of the invention, the cubicboron nitride particle size is preferably 20 micron or less. The use ofsuch fine grained particles, in woodworking applications, revealed forsome applications a more than tenfold increase in performance comparedto conventional carbide materials. Whilst polycrystalline diamond has aneven higher wear resistance, it was found that the material of theinvention wears by progressive rounding of the edge whereaspolycrystalline diamond wears by micro-chipping, which is a disadvantagein certain applications such as woodworking. The fine-grainmicrostructure of the abrasive material of the invention also promotessmooth and rapid electric discharge machining characteristics.

[0022] The abrasive material of the invention is thus particularlysuited as a tool material for a variety of machining operations ofmoderately abrasive metallic and non-metallic workpieces andparticularly of wood and like lignocellulosic products. The abrasivematerial of the invention combines improved machining performance overconventional tungsten carbide whilst also retaining the major positiveaspects of conventional carbide such as high impact resistance, goodbrazeability and ease of tool preparation, for instance through grindingand electric discharge machining.

[0023] The abrasive material of the invention is produced by a methodcomprising providing a mixture of a mass of discrete carbide particlesand a mass of cubic boron nitride particles, and subjecting the mixtureto elevated temperatures and pressure conditions at which the cubicboron nitride is crystallographically stable and at which substantiallyno hexagonal boron nitride is formed, in the presence of the bondingmetal or alloy capable of bonding the mixture into a coherent, sinteredmaterial.

[0024] The abrasive material produced must be substantially free ofhexagonal boron nitride. The presence of a significant quantity ofhexagonal boron nitride reduces the abrasive wear resistant propertiesof the material. In producing the material, it is important thatconditions are chosen which achieve this.

[0025] The carbide particles may be any carbide particles used in themanufacture of conventional cemented carbides. Examples of suitablecarbides are tungsten carbide, tantalum carbide, titanium carbide,niobium carbide and mixtures thereof. The presence of titanium carbide,niobium carbide and tantalum carbide can enhance the machineability ofcertain steels, for instance carbon-steels, free-machining steels, toolsteels, ferritic steels and alloy steels.

[0026] The carbide particles may have a size greater than, less than orequal to the size of the cubic boron nitride particles.

[0027] The bonding metal or alloy may be any bonding metal or alloy usedin the manufacture of conventional cemented carbides. Examples arecobalt, iron, nickel and alloys containing one or more of these metals.

[0028] The bonding metal or alloy content of the abrasive material ofthe invention is preferably an amount of from 3% to 15% inclusive byweight of the abrasive material. If a highly wear resistant material isdesired, the metal content will be low. For higher impact resistance, asfor instance required in interrupted cutting or circular sawing, ahigher metal content is required to increase toughness of the abrasivematerial.

[0029] The bonding metal or alloy is preferably provided in powder form,but may also be added in the form of an organic precursor, a metal oxideor a salt precursor that is subsequently pyrolised and/or reduced toresult in finely dispersed metal.

[0030] The bonding metal or alloy may-be mixed with the carbideparticles and with the cubic boron nitride particles and the mixture maythen be sintered as such, or the mixture may first be cold-pressed toproduce a weak but coherent body prior to sintering.

[0031] Alternatively, the bonding metal or alloy may be supplied in theform of a separate layer adjacent to the cubic boron nitride-carbidemixture and infiltrated during the high temperature/high pressuretreatment step.

[0032] The sintering of the mixture of carbide and cubic boron nitrideparticles and the bonding metal or alloy preferably takes place at atemperature of from 1200° C., preferably at temperature in the range offrom 1200° C. to 1600° C. inclusive, and at a pressure of from 30 to 70kbar inclusive.

[0033] This step is carried out under controlled non-oxidizingconditions. The non-oxidizing conditions may be provided by a vacuum,for example a vacuum of less than 1 mbar.

[0034] The sintering of the mixture of carbide and cubic boron nitrideparticles and the bonding metal or alloy may be carried out in aconventional high temperature/high pressure apparatus. The mixture maybe loaded directly into the reaction capsule of such an apparatus.Alternatively, the mixture may be placed on a cemented carbide supportor a recess formed in a carbide support, and loaded in this form intothe capsule.

[0035] In a preferred method of the invention, the carbide particles,the cubic boron nitride particles and the bonding metal or alloy havevolatiles removed from them prior to sintering, e.g by heating them in avacuum. These components are preferably then vacuum sealed by, forexample, electron beam welding prior to sintering. The vacuum may, forexample, be a vacuum of 1 mbar or less and the heating may be atemperature in the range of 500° C. to 1200° C. inclusive.

[0036] A further aspect of the invention is a method of abrading aworkpiece selected from wood and other lignocellulosic materials whichincludes the steps of providing a tool having a tool component or insertcomprised of the abrasive material as described above, providing theworkpiece, bringing the tool component or insert into contact with theworkpiece, and advancing the tool component or insert into the workpiecein an abrading manner.

[0037] Abrading in the context of the specification means cutting,drilling, routing, polishing, or any similar such abrading action. Thisaction may take various forms, known in the art, such as rotation of thecutting edge or point, reciprocating movement of the cutting edge orpoint or the like. Of course, the abrading action can also be achievedby maintaining the edge or point stationary and moving the workpiece.

[0038] The workpiece is selected from wood and other lignocellulosicmaterials. Examples of wood and other lignocellulosic products arenatural wood, either soft or hard wood, laminated and non-laminatedchipboard and fibreboard, which contain wood chips or fibre bonded bymeans of binders, hardboard which is compressed fibre and sawdust, andplywood.

[0039] Examples of tools which may be used for abrading are multi-tiprotary tools such as circular saws, profile cutters, end mills, millingcutters and routers. The tool component or insert may be any suitabletool component or insert for use in such tools.

[0040] The invention will now be described in more detail with referenceto the following examples.

EXAMPLE 1

[0041] In order to evaluate the effect of cubic boron nitride (c-BN)grain size, varying amounts of cubic boron nitride in varying particlesize were blended with a fine grained mixture of tungsten carbide in thesize range 1 to 2 micron, containing 11 weight percent of cobalt. Thepowders were thoroughly mixed in a planetary ball mill to achieve ahomogeneous blend of the materials. The blends were uniaxially compactedto form coherent pellets. The pellets were loaded into a metal canisterand subsequently outgassed under vacuum at 1100° C. and sealed byelectron beam welding. The sealed containers were loaded into thereaction capsule of a standard high pressure/high temperature apparatusand the loaded capsules placed into the reaction centre of thisapparatus. The contents of the capsule were exposed to a temperature ofapproximately 1450° C. and a pressure of 50 kbar. These conditions weremaintained for 10 minutes. After completion of the treatment,well-sintered, hard and wear resistant materials were recovered from thecanister.

[0042] The wear resistance of the materials was tested using a turningtest where silica flour filled epoxy resin was machined using thefollowing conditions: Sample format 90° quadrant 3,2 mm thick Toolholder neutral Rake angle 0° Clearance 6° Cutting speed 10 m/min Depthof cut 1.0 mm Feed rate 0.3 mm/rev Test duration 30 s

[0043] The maximum flank wear of the materials is shown in FIG. 1. Thegraph shows that the highest wear resistance is achieved using a finegrained c-BN starting particle size.

EXAMPLE 2

[0044] In order to assess the effect of cobalt content and c-BN content,a new batch of materials was prepared using the method of Example 1. Thec-BN grain size was kept constant at 1-2 microns. The same turning testwas used as in Example 1 with the duration increased to 60 seconds so asto improve the resolution of the measurement. The results of the testare shown in FIG. 2.

[0045] It can be seen that the wear resistance is increased withincreasing c-BN content and favoured by a lower cobalt content.

EXAMPLE 3

[0046] Selected samples from Examples 1 and 2 were submitted for toolpreparation. It was found that even with a relatively high c-BN content,the samples were easy to grind. Using a wheel normally used forpolycrystalline diamond, the composite materials ground at a similarrate as cemented tungsten carbide and achieved an excellent edge qualityof a similar standard as that of a typical cemented carbide tool. Allmaterials were easy to grind with the finer grained materials showingslight advantages. Electric discharge machining was also fast andproblem free. The materials generally cut at a similar rate as cementedcarbide. Rates were seen to increase with decreasing c-BN grain contentand grain size.

EXAMPLE 4

[0047] A number of braze alloys were evaluated to determine the brazestrength of typical materials of the invention. It was found that thebraze strength is approximately proportional to the volume fraction ofcemented carbide present in the material. All materials investigatedwere brazeable to both tungsten carbide and steel.

[0048] Using the method described in Example 1 a sintered material(designated Cl) was prepared form a powder mixture of 14,9 wt % cubicboron nitride, 75,7 wt % tungsten carbide and 9,4 wt % cobalt, all inthe size range 1 to 2 microns, and subjected to a matrix of brazingexperiments. The resulting braze shear strengths of this material and acomparable cemented carbide are shown in Table 1. It can be seen thatthe braze strength is related to the volumetric amount of c-BN presentTABLE 1 Braze Shear Strength (MPa) Cemented Cemented carbide C1 brazedcarbide brazed to C1 brazed to cemented brazed to cemented Braze Alloyto steel carbide steel carbide Degussa CH1 134.9 194.9 260.3 291.6Degussa CH2 166.7 167.4 181.2 De Beers DBF1 108.0 468.8 352.1 Degussa21/80  40.7 129.8 143.3 143.3 Degussa 4900 268.7 363.0 Easy-Flo 45 172.4344.7

EXAMPLE 5

[0049] The material designated C1 in Example 4 was employed for routingtests on medium density board and comparisons were made withpolycrystalline diamond, high speed steel and tungsten carbide tools.Single flute routers were prepared with a nominal diameter of 13 mm. A0° top rake cutting geometry was used and relative wear rates werecompared. The cutting speed was 1000 m/min obtained using a rotationalspeed of 21,120 rpm.

[0050] Panels with a geometry of approximately 1000 mm×300 mm wereprepared. Cutting was carried out on each board in an “upcutting” modeand the cut pattern was arranged so that 100 m of cut could be obtainedfrom each panel. The routers penetrated the panels to a depth of 10 mmand a constant feed rate of 0,1 mm/tooth (2122 mm/min) was used in alltests. At each pass the tool in-feed was 2 mm. Vacuum extraction wasused to remove the wood dust. The cutters were removed periodically andthe flank wear produced on the cutting edges measured.

[0051] Due to the low abrasiveness of the medium density fibreboard itwas difficult to monitor the wear produced on the more resistantcutters. However, the high speed steel wore rapidly reaching a wear scarwidth of 0,2 mm after machining a distance of less than 50 m. The othermaterials were tested up to a total machining distance of 3000 m. Theresulting flank wear scar widths were: Cemented carbide 0.135 m C1 0.063mm Polycrystalline diamond 0.037 mm

[0052] The appearance of the wear-scars after machining were examinedusing scanning electron microscopy. It was found that the wear of the Cland the cemented carbide tools was by progressive rounding whereas thepolycrystalline diamond tool showed some evidence of micro-chipping.

EXAMPLE 6

[0053] The experiments described in Example 5 were repeated under thesame conditions using chipboard as the workpiece.

[0054] With this more abrasive workpiece it was found that high speedsteel wore very rapidly within one or two metres and cemented carbideshowed a flank wear greater than 0,15 mm after only 100 m of cut. Afterthis amount of flank wear the cutting process became unacceptably noisyand the laminate surface was heavily chipped by the dull tool. Thematerial designated C1 in Example 4, on the other hand, showed asignificantly lower wear rate and it was found that its tool life to aflank wear of 0,15 mm is of the order of 1500 m. This is a 15-fold lifeimprovement over cemented carbide. The wear rate of polycrystallinediamond was also measured for comparison. PCD wear resistance was sohigh that it was not practical to run the tools to the tool life endpoint. A tool life of at least an order of magnitude higher than that ofC1 can be expected.

[0055] Chipboard is characterised by a plastic laminate on top ofapproximately 1 mm thick, high density surface layers and a low densitycore. Wear scar analysis revealed that the greatest tool wear took placein the high density region near the surface of the board and that it isboth this high density chipboard layer and the resin impregnatedlaminate which produce most wear. Negligible wear is produced by the lowdensity interior of the board.

[0056] Wear scar analysis after completion of the test also showed thatthe edge of the material of the invention wears by progressive roundingrather than edge chipping. The wear mechanism is appreciated in the woodworking industry since tools then impart a smooth finish to the wood asthey wear without leaving “witness” marks. Tools which are too brittle,chip and leave unacceptable marks on the cut surface which then mayrequire subsequent sanding. In the case of polycrystalline diamond, weartakes place by micro-chipping rather than uniform progressive wear andthis can be a problem in certain applications. The progressive roundingrather than chipping wear of the material of the invention coupled withits enhanced wear resistance is one of its major advantages.

EXAMPLE 7

[0057] The material designated C1 in Example 4 was evaluated in the edgemilling of fibre cement board and comparisons were made withpolycrystalline diamond and tungsten carbide tools. The cutter bladedesign is shown in FIG. 3 and the machining conditions were: Depth ofCut 125 mm jointing/rebating head Depth of Cut 1 mm Board feed 10 m/minSpindle 3700 rpm Width of Cut 2 mm

[0058]FIG. 4 shows tool flank wear as a function of linear metresmachined. The ranking is similar as that found for the machining ofchipboard in the previous example. Again it was found that the materialof the invention wore in a smooth progressive fashion whereaspolycrystalline diamond showed evidence of micro-chipping.

EXAMPLE 8

[0059] The experiment described in Example 7 was repeated with amaterial of lower cobalt content. The volume fraction of c-BN in thematerial was kept the same as that of the material designated C1 inExample 4, but the cobalt content of the cemented carbide was reduced to6 weight percent.

[0060] The new material gave an approximately 30% improvement inperformance over C1.

EXAMPLE 9

[0061] The material designated C1 in Example 4 was tested in thecircular sawing of cast iron swarf in epoxy resin.

[0062] Fifty pieces with dimensions of 6 mm×4 mm×2 mm were brazed to asteel saw blank (305 mm diameter, 3 mm thick) using a 50% silver lowtemperature brazing alloy. The cemented carbide saw had 100 teeth incomparison. No reduction in the feed rate was used to compensate for thehigher tooth loading.

[0063] Whilst some teeth of the saw blade with the material of theinvention broke in operation, resulting in a reduced tool lifeas-compared with the standard WC blade, the cut was of very goodquality. The amount of wear visible on those teeth which had survivedwas significantly less than for a comparable WC material.

EXAMPLE 10

[0064] The material designated Cl in Example 4 was evaluated as acutting tool for Inconel 718. The experimental parameters were asfollows: Material Inconel 718, Solution treated Insert Format SPGN090212F Cutting geometry: top rake −6°, i.e. positive insert in negativetoolholder effective clearance 13° approach 45° Cutting speed 50 m/minFeed rate 0.2 mm/rev Depth of cut 1.0 mm Coolant yes

[0065] After 40 minutes of cutting the flank wear was approximately 0,3mm. A small amount of notching was observed but this was less than thatproduced on cemented carbide tools. The surface finish produced on thecomponent was said to be of grinding quality. The normal cutting speedand feed rate used with cemented carbide is 25 m/min and 0,4 mm/rev,respectively. At this speed, a flank wear of 0,5 mm and a notch of 1,5mm is produced in approximately 15 minutes. From these results, theperformance can be seen to be significantly better than of conventionalcemented carbide.

1. An abrasive and wear resistant material comprising a mass of carbideparticles, a mass of cubic boron nitride particles, and a bonding metalor alloy bonded into a coherent, sintered form, wherein: the cubic boronnitride particle content of the material is from 10% to 18% inclusive byweight; the particle size of the cubic boron nitride is 20 micron orless; and the material is substantially free of hexagonal boron nitride.2. A material according to claim 1 wherein the carbide particles areparticles selected from the group consisting of tungsten carbide,tantalum carbide, titanium carbide, niobium carbide and mixturesthereof.
 3. A material according to claim 1 or claim 2 wherein thebonding metal or alloy is selected from the group consisting of cobalt,iron, nickel and alloys containing one or more of these metals.
 4. Amaterial according to any one of claims 1 to 3 wherein the bonding metalor alloy content of the material is from 3% to 15% inclusive by weightof the material.
 5. A method of producing an abrasive and wear resistantmaterial including the steps of providing a mixture of a mass ofdiscrete carbide particles and a mass of cubic boron nitride particles,the cubic boron nitride particles being present in the mixture in anamount such that the cubic boron nitride content of the material is from10% to 18% inclusive by weight, and wherein the cubic boron nitrideparticles have a particle size of 20 micron or less; and subjecting themixture to elevated temperature and pressure conditions at which thecubic boron nitride is crystallographically stable and at whichsubstantially no hexagonal boron nitride is formed, in the presence of abonding metal or alloy capable of bonding the mixture into a coherent,sintered material.
 6. A method according to claim 5 wherein the carbideparticles are particles selected from the group consisting of tungstencarbide, tantalum carbide, titanium carbide, niobium carbide andmixtures thereof.
 7. A method according to claim 5 or claim 6 whereinthe bonding metal or alloy is selected from the group consisting ofcobalt, iron, nickel and alloys containing one or more of these metals.8. A method according to any one of claims 5 to 7 wherein the bondingmetal or alloy content of the material is from 3% to 15% inclusive byweight of the material.
 9. A method according to any one of claims 5 to8 wherein the bonding metal or alloy is provided in powder form or isadded in the form of an organic precursor, a metal oxide or a saltprecursor that is subsequently pyrolised or reduced to result in finelydispersed metal.
 10. A method according to any one of claims 5 to 9wherein the bonding metal or alloy is mixed with the mass of discretecarbide particles and the mass of cubic boron nitride particles and themixture is then sintered.
 11. A method according to any one of claims 5to 9 wherein the bonding metal or alloy is mixed with the mass ofdiscrete carbide particles and the mass of cubic boron nitrideparticles, the mixture is then cold-pressed to produce a weak coherentbody, and the body is then sintered.
 12. A method according to any oneof claims 5 to 9 wherein the bonding metal or alloy is supplied in theform of a separate layer adjacent to the mixture of the mass of discretecarbide particles and the mass of cubic boron nitride particles andinfiltrated when the mixture is subjected to the elevated temperatureand pressure conditions.
 13. A method according to any one of claims 5to 12 wherein the elevated temperature and pressure conditions are attemperature of from 1200° C. to 1600° C. inclusive and a pressure offrom 30 to 70 kbar inclusive.
 14. A method of abrading a workpieceselected from wood and other lignocellulosic materials including thesteps of providing a tool having a tool component or insert comprised ofan abrasive and wear resistant material comprising a mass of carbideparticles, a mass of cubic boron nitride particles, and a bonding metalor alloy, bonded into a coherent, sintered form, wherein the cubic boronnitride particle content of the material is from 10% to 18% inclusive byweight, the particle size of the cubic boron nitride is less than 20micron or less, and the material is substantially free of hexagonalboron nitride; providing the workpiece; bringing the tool component orinsert into contact with the workpiece and advancing the tool componentor insert into the workpiece in an abrading manner.
 15. A methodaccording to claim 14 wherein the carbide particles are particlesselected from the group consisting of tungsten carbide, tantalumcarbide, titanium carbide, niobium carbide and mixtures thereof.
 16. Amethod according to claim 14 or claim 15 wherein the bonding metal oralloy is selected from the group consisting of cobalt, iron, nickel andalloys containing one or more of these metals.
 17. A method according toany one of claims 14 to 16 wherein the bonding metal or alloy content ofthe material is from 3% to 15% inclusive by weight of the material.